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net: ch9200: fix uninitialised access during mii_nway_restart

Browse source 
commit 9ad0452c0277b816a435433cca601304cfac7c21 upstream.

In mii_nway_restart() the code attempts to call
mii->mdio_read which is ch9200_mdio_read(). ch9200_mdio_read()
utilises a local buffer called "buff", which is initialised
with control_read(). However "buff" is conditionally
initialised inside control_read():

        if (err == size) {
                memcpy(data, buf, size);
        }

If the condition of "err == size" is not met, then
"buff" remains uninitialised. Once this happens the
uninitialised "buff" is accessed and returned during
ch9200_mdio_read():

        return (buff[0] | buff[1] << 8);

The problem stems from the fact that ch9200_mdio_read()
ignores the return value of control_read(), leading to
uinit-access of "buff".

To fix this we should check the return value of
control_read() and return early on error.

Reported-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=3361c2d6f78a3e0892f9
Tested-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Fixes: 4a476bd6d1 ("usbnet: New driver for QinHeng CH9200 devices")
Cc: stable@vger.kernel.org
Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
Link: https://patch.msgid.link/20250526183607.66527-1-qasdev00@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Qasim Ijaz 2025-05-26 19:36:07 +01:00 • committed by Greg Kroah-Hartman
commit 119766de49
1 changed files with 5 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

7
drivers/net/usb/ch9200.c
View file

@ -180,6 +180,7 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
{
struct usbnet *dev = netdev_priv(netdev);
unsigned char buff[2];
int ret;
netdev_dbg(netdev, "ch9200_mdio_read phy_id:%02x loc:%02x\n",
phy_id, loc);
@ -187,8 +188,10 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
if (phy_id != 0)
return -ENODEV;
control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
CONTROL_TIMEOUT_MS);
ret = control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
CONTROL_TIMEOUT_MS);
if (ret < 0)
return ret;
return (buff[0] | buff[1] << 8);
}